What best describes memory cells?

• A. A red blood cell.
• B. A type of cell that recognizes pathogens and can quickly produce antibodies upon re-exposure.
• C. A virus particle.
• D. A bacterium.

Answer: (B)

Memory cells are a subset of immune cells that persist after an initial infection to “remember” the invader. They stay in the body and respond quickly if the same pathogen is encountered again, producing a faster and stronger response. In particular, memory B cells recognize the pathogen and can rapidly differentiate into antibody-secreting cells upon re-exposure, yielding antibodies sooner than during the first encounter. The other options describe things that are not immune memory cells: red blood cells carry oxygen; a virus particle is not a cell; a bacterium is a microbe, not a memory cell.